A body travels 102.5 m in $\mathrm { n } ^ { \text {th} }$ second and 115.0 m in $( \mathrm { n } + 2 ) ^ { \text {th} }$ second. The acceleration is :\\
(1) $6.25 \mathrm {~m} / \mathrm { s } ^ { 2 }$\\
(2) $12.5 \mathrm {~m} / \mathrm { s } ^ { 2 }$\\
(3) $9 \mathrm {~m} / \mathrm { s } ^ { 2 }$\\
(4) $5 \mathrm {~m} / \mathrm { s } ^ { 2 }$