An aircraft has the following characteristics:

Empty mass $=40,000$kg$,$ fuel mass $=10,000$kg$,$ overall propulsion efficiency $=0\mathrm{.}25$

Fuel energy$/$mass $=43$ MJ$/$kg$,$ cruise lift coefficient $=1\mathrm{.}4,$ cruise drag coefficient $=0\mathrm{.}078$

a$)$ Calculate the range. Assume that all fuel is consumed.

b$)$ How much additional fuel must be caried to extend the range by $25\%?$