If 15% of 30% of 50% of a number is 90, then what is the number?

A. 4000
B. 3050
C. 4400
D. 4500
E. None of these
Let the number be a
Given, 15/100 * 30/100 * 50/100 * a = 90
=> 3/20 * 3/10 * 1/2 * a = 90
=> a = 10 * 20 * 10 * 2 = 4000.