ABC26GN5576 · Tabulation

Total production of $B$ from 2006 to 2011 $$\begin{aligned} & =\left[\begin{array}{r} \left(750 \times \frac{4}{5}\right)+\left(800 \times \frac{7}{8}\right)+\left(600 \times \frac{4}{3}\right) \\ +\left(550 \times \frac{12}{11}\right)+\left(700 \times \frac{13}{14}\right)+\left(650 \times \frac{14}{13}\right) \end{array}\right] \text { tonnes } \\ & =(600+700+800+600+650+700) \text { tonnes } \\ & =4050 \text { tonnes. } \end{aligned}$$ ∴ Average production $=\frac{4050}{6}$ tonnes = 675 tonnes.