$.$ Each end of a string with $=5\mathrm{.}40$ g$/$m is attached to two opposite walls.

The distance between the walls is $$ the length of the string. A block of

mass m hangs from the middle of the string. Neglect the mass of the string in

calculating the tension.

a$.$ Find an expression for the transverse wave speed in the string as a

function of the mass of the block. Assume that m is measured in kg

and v is measured in m$/$s$.$

b$.$ What is the mass of the block $($in kg$)$ if the wave speed is $70\mathrm{.}0$ m$/$s$?$