We have a problem with three different state of the ratio of flow velocity to speed of sound.
That is,
a) Mach number to evaluate is 0.2, that mean we have a subsonic state.
The equation here for lift coefficient is,
where should be expressed in Rad.
So replacing in equation for subsonic state,
b) In this situation we have a transonic state, so we need to use the Prandtl-Glauert rule,
c) For this case we have a supersonic state, so we use that equation,