the product's unit digit is the unit digit of 8*b. Therefore, the units digit should be the units digito of a multiple of 8

8*1=8 -> 8
8*2=16 -> 6
8*3 =24 -> 4
8*4 = 32 -> 2
8*5 =40 - > 0
8*6 = 48 -> 8 ..and the cycle repeats

so, we have 0,2,4,6,7 as the possible units digits and thus answer choice D is eliminated

4a8 * 60 + 4a8 * b = x

let's find the upper bound value i.e. the value the answer should certainly be less than
--> 500*70 = 3500 -> ans choice E is eliminated

now let's find the lower bound value
400*60 = 24000 -> ans choices A & B are eliminated

So, now we only have answer choice C as a possible answer and thefore this is the answer.

Correct.

thanks!

Nice! So you just rounded up to 500 and 70 to get the upper bound and likewise (rounded down) for the lower bound, correct? Good strat

Awesome solution! Thanks.