how many 4 digit numbers are there , if it is known that the first digit is odd , the second is odd , the third is prime , the fourth ( units digit ) is divisible by 3 , and the digit 1 can be used only once ?
"4 options for the first digit : 1 , 3 , 5 , 7 , 9 ; 5 options for the second digit : 1 , 3 , 5 , 7 , 9 ; 4 options for the third digit : 2 , 3 , 5 , 7 ; 4 options for the fourth digit : 0 , 3 , 6 , 9 . four digit # possible without the restriction ( about the digit 2 ) : 5 * 5 * 4 * 4 = 400 numbers with one 1 - s , 1 x 1 x 1 * 1 * 4 * 4 = 16 . thus there are 400 - 16 = 384 such numbers . answer : c ."
subtract(multiply(multiply(add(4, const_1), add(4, const_1)), multiply(4, 4)), multiply(multiply(add(4, const_1), add(4, const_1)), 4))