If the first term of an A.P. is 3 and the sum of its first 25 terms is equal to the sum of its next 15 terms, then the common difference of this A.P. is
(1) $\frac { 1 } { 6 }$\\
(2) $\frac { 1 } { 5 }$\\
(3) $\frac { 1 } { 4 }$\\
(4) $\frac { 1 } { 7 }$