A small block with mass .250kg is attacked to a string passing through a hole in a frictionless, horizontal surface. The block is originally revolving in a circle with a radius of .800m about the hole with a tangential speed of 4.00m/s. The string is then pulled slowly from below , shortening the radius of the circle in which the block revolves. The breaking strength of the string is 3.00 N. What is the radius of the circle when the string breaks?