The number of terms in an A.P. is even ; the sum of the odd terms in it is 24 and that the even terms is 30 . If the last term exceeds the first term by $\;10 \large\frac{1}{2}\;$, then the number of terms in the A.P. is :

Question

$(a)\;4\qquad(b)\;8\qquad(c)\;12\qquad(d)\;16$