A block of mass $0.80 kg$ is attached to a cord passing through a hole in a horizontal frictionless surface. The block is originally revolving at a distance of $0.30 m$ from the hole with a speed of $0.80 m/s$ The cord is pulled from below the hole, shortening the radius of circle in which the block revolves to $0.10 m$. At this new distance the speed of block is $2.40 m/s$. How much work is done by person who pulled the cord?

Question

$$(a)\;1.50 \;J\quad (b)\;2.05\;J \quad (c)\; 4.25 \;J \quad (d)\;1.05\;J$$