need help with this one

For this question, a straight line is the closest, and will always be.
To find the length of the line AC, we can see that it is the hypotnuse of a right triangle with the height of 8 and a base of ( using the pythagorean theorem) √261. Now, we square 8, 64, and the √261, 261, and find the sum.
64+261=325
The answer is square root of 325, and by taking 5 out, the final answer should be 5√13
Thats the diagonal through the prism.
Diagonal of the base = sqrt ( 15^2 + 6^2) = sqrt 261
AC = sqrt ( 261 + 8^2)
= sqrt 325
sqrt ( 25 * 13)
= 5 sqrt13 m answer
Its B