The figure shows a $5 \mathrm{kg}$ ladder hanging from a string that is connected with the ceiling and is having a spring balance connected in between. A boy of mass $25 \mathrm{kg}$ is climbing up the ladder at acceleration $1 \mathrm{m} {\mathrm{s}}^{-2}$. Assuming the spring balance and the string to be massless and the spring to show a constant reading, the reading of the spring balance is (Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)