Recap - Spring Launcher

A pinball plunger spring is pulled back $0.05\ \mathrm{m}$ and launches a $0.1\ \mathrm{kg}$ ball up the smooth table, tilted at $15^\circ$. When the ball is $0.5\ \mathrm{m}$ higher than where it started, it still moves at $3\ \mathrm{m/s}$. The picture shows the ball twice: at the start and at that moment. Draw the forces on it at that moment, from the dot, then find the spring constant $k$ of the plunger spring.