I think the answer is B).

Statement 1 tells us that the score is between 50 and 90. Taking two extremes, 50 and 59, we see that the bonus on 50 would be 10, which is 20% of 50, so the bonus would be greater than 17% of the base score.

59 would still yield a bonus of 10 on the base score, but 0.17*59 is actually 10.03, so the bonus would not be greater than 17% of the base score, hence INSUFFICIENT, since we can prove both scenarii possible.

Statement 2 basically tells us that the last score was between 80 and 89 included (tens digit 8, times 2), so again we test for extremes.
In the case of 80, 16 points is again 20% of the base score, which is greater than 17% of 80.
In the case of 89, 0.17*89=15.13, so again the bonus is greater than 17% of the base score.

This is enough information to determine that the bonus is greater than 17% of the base score, hence SUFFICIENT, or B).

When the GMAT asks for "is x greater than" kind of questions, it's usually good to test extremes.