If you don't understand load lines yet, you'll need to gain that understanding in order to illustrate it.
The class of operation will determine how much power will be dissipated by the valve itself during the transition period of the AC output signal (i.e. the period in which the signal is transitioning from positive to negative and vice versa). The load impedance and B+ voltage will determine how much power will be dissipated by the load (i.e. the OT) at the peaks of the swing.