Compute the value of summation using the composition of set

Question

Q. If \(\psi = \bigl\{ \phi_i \:|\: \phi_i =\frac{\sum_{\eta=i}^{15}}{2}=\gamma \:; i,\gamma \in N \& \: i≤10 \bigr\}\), then compute the value of \(\sum\psi_o\), where \( \psi_o \in \psi\).