Let a be the sum of the (decimal) digits of 314159. let b be the sum of the digits of a. in this problem, we aim to compute the sum of the digits of b, without the use of a calculator. (a) note that 31 < 102 . use this to give a crude upper bound of the form 314159 < 10n . under this upper bound, what is the most a could be? with this upper bound on a, what is the most b could be? with this upper bound on b, show that b’s digit sum is at most 12.