求解GWD里的3道数学题。。谢谢各位了！

1) If 10^50 – 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer?
A. 424    B. 433 C. 440 D. 449 E. 467

2)A positive integer n is said to be “prime-saturated” if the product of all the different positive prime factors of n is less than the square root of n.  What is the greatest two-digit prime-saturated integer?
A. 99    B. 98       C. 97    D. 96    E. 95

3) A photographer will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.How many such arrangements of the 6 people are possible?
A.5    B.6    C.9    D.24 E.36