how much to secure the border?

About $15 million. That's with an m not a b. 

Concertina Wire Price per Meter - Affordable Security Solutions

The US-Mexico border is about 3,100 km long. At $5 per meter, that works out to about $15 million. That amount is chump change when it comes to federal spending. 

It won't stop everyone, but it will slow down 99% enough to be captured by border patrols. 

Add to the wire anything that rattles, like tin cans. That's an old trick to alert passing patrols. 

 

meanwhile in Africa

Here's what foreign aid pays for:

I exaggerate somewhat, but the main result of foreign aid is population growth. Perhaps someday Africa will industrialize to a similar level as Europe or North America. I doubt it. In any case, Africa is and will be dependent on food aid and food imports, as well as imports of fuel, fertilizer, and machinery. 

The above screenshot is from the 7:42 mark of this video:

The Collective African Culture Is Broken

Elsewhere

Tanzanian President Magufuli pardons child rapists

The orphanage director I worked with in Tanzania tried unsuccessfully to get permission for a pregnant girl to return to school as she was less than a year from graduating. 

 

lingua franca

 

game over

 

upstream

 

The Goldbach Conjecture and large primes

Mathematicians like exact solutions. Engineers are satisfied with good approximations. Let's see if there's a pattern among the largest primes smaller than a certain even number

10 7

100 97

1000 997

2000 1999 

5000 4999 

10000 9973

100000 99991

The corresponding percents are 70, 97. 99.7, 99.95, 99.98, 99.73, and 99.99.

Thus, we can infer that for even numbers greater than 100,000, the largest prime smaller than that number will be about 99% of that number. 

So, if we want to find large primes, one way would be to multiply a large even number by 0.99 and using the Miller-Rabin primality test. There is another primality test I have worked on that uses the Collatz Conjecture. It works by using the suspected prime as the seed value for the Collatz Conjecture and then checking to see if the first odd result (that is not a multiple of 5) is prime. 

Another way would be to subtract small known primes from the even number and checking if the result is prime. 

In the cases of 10,000 and 100,000, the largest prime smaller than either does not form a Goldbach pair. So actually, what we really want to know is: what is the largest prime smaller than an even number that forms a Goldbach pair?

I suspect many such pairs contain 3, 7, 13, 17, etc as the smaller prime. 

Turing test