What am i missing - adds up to 99?
MC (20)
21 - Gravity prac (6)
22 - Solenoid (6)
23 - Tower (4)
24 - Bands ie. conductor (5)
25 - Transistor (7)
26 - Power transmission (6)
27 - Projectile (4)
28 - Einstein & criteria for a theory (6)
29 - Loudspeaker (5)
30 - Charged particles...