Energy, work and power — practice question

A block is attached to one end of a light inextensible string. The string is inclined at an angle of $\theta^\circ$ to the horizontal. The tension in the string is $20\,\text{N}$. The string moves the block across a horizontal surface at a steady speed of $1.5\,\text{m s}^{-1}$ for $12\,\text{s}$. The work done by the tension in the string is $50\,\text{J}$.