The puzzle below is a cross number puzzle, similar to a crossword puzzle except that the entries are numbers. Enter one digit per square. The thick heavy line is a separator.
ACROSS:
a. A prime number
c. The sum of digits of a across
DOWN:
a. Square of the sum of the digits of b down
b. A prime number
I am confused on how to solve this problem. I do understand from across problem a must be a prime number so a= 2, 3, 5 or 7. It can't be anything higher because it has to be one digit. c is sum of digits of a and b across. Since it can only be one digit, c must be c= 2, 3, 4, 5, 6, 7, 8, or 9
Then for down, the square of the sum of digits of b down would equal a, so (b+c)^2 is going to equal a down. However, does the box under a and across from c - will it have a number too? I think it would have to because two numbers squared can't equal any of the above digits...
Finally B is a prime number so b= 2, 3, 5, or 7
Unsure of where to go from here, because there are so many different paths to attempt and I am unsure of where to go from here.

I have to do this problem for a math class. My teacher said that A across is a 2 digit number meaning the box that has an A in it and the box that has a B in it as well. I was not able to figure out the answer yet but I believe that A across must be either 43 or 61 making B down either 37 or 17. Hope this helped!