Data Sufficiency

Every member of a certain club volunteers to contribute equally to the purchase of a $60 gift certificate. How many members does the club have?

(1) Each member's contribution is to be $4
(2) If 5 club members fail to contribute, the share of each contributing member will increase by $2.

Statement(1):
sufficient to answer.
number of members = (total contribution)/(individual contribution) = 60/4 = 15

Statement(2):
Let the number be x, which implies each contribution must be 60/x, if all members contribute equally.
"If 5 members fail to contribute, the share of each contributing members will increase by 2" => (x-5)(60/x - 2) = 60
This yields two values for x. But without finding the values, we cannot take any decision.
After solving the equation, we get x = 6 or -10
Negtive value for x can be neglected, as it represents number of members. As there is no ambiguity in the value of x, statement(2) alone is also sufficient

Answer "D"