One of the weapons being considered

One of the weapons being considered for the “Star Wars” antimissile system is a laser that could destroy ballistic missiles. When a high-power laser is used in the Earth’s atmosphere, the electric field can ionize the air, turning it into conducting plasma that reflects the laser light. In dry air at 0°C and 1 atm, electric breakdown occurs for fields with amplitudes above about 3.00 MV/m.
(a) What laser beam intensity will produce such a field?
(b) At this maximum intensity, what power can be delivered in a cylindrical beam of diameter 5.00 mm?