Mathematics - find the smallest integer value of n for which 84n is a multiple of 35?

84 * 5 = 420
420 / 35 = 12

n = 5 was actually my first guess, as 5 * 4 (the last digit in 84) ends in a 0 and every multiple of 35 ends either in a 0 or a 5 and there is no product of 4 which has a 5 as its last digit.