Solve the Problem $$\int _ { 0 } ^ { a } \int _ { 0 } ^ { 10 ( 1 - x / a ) } \int _ { 0 } ^ { 3 ( 1 - x / a - y / 10 ) } d z d y d x = 15$$

Multiple Choice

Solve the problem.
-Solve for a:
$$\int _ { 0 } ^ { a } \int _ { 0 } ^ { 10 ( 1 - x / a ) } \int _ { 0 } ^ { 3 ( 1 - x / a - y / 10 ) } d z d y d x = 15$$

A) $a = 3$
B) $a = 2$
C) $a = \frac { 5 } { 2 }$
D) $a = \frac { 18 } { 5 }$