(a)  when t = 0,   n = 1000 x 2⁰ = 1000 x 1 = 1000

(b) when t = 2,  n = 1000 x 2² = 1000 x 4 = 4000

% increase of bacteria cultured  =  (4000-1000)/1000 x 100% = 300%