An aircraft is flying at $400$ mi$/$hr at $25,000$ ft and has a requirement to accelerate at $3$ ft$/$s$^2$ in level flight.

The aircraft has the following characteristics:

Thrust $=9000$ lb

Drag $=6500$ lb

Weight of aircraft $+$ fuel$+$ occupants $=25,000$ lb$.$

a$)$ How much additional weight can the aircraft carry and meet the acceleration requirement?

b$)$ How does this answer change if the drag is reduced by $5\%?$