15 Each week, Henri records the number of units of gas used in his house and the mean temperature outside. Ten of his results are shown in the table. (a) On the grid, complete the scatter diagram. The first five results have been plotted for you. (b) What type of correlation does your scatter diagram show? (c) Draw a line of best fit on the grid. (d) Use your line of best fit to estimate the number of units used for one week when the mean temperature outside is 7.6 °C.