Find the missing length

The diagram shows a 7cm by 6cm rectangle based pyramid. all the diagonal sides - ta, tb, tc and td are length 10cm. m is midpoint of rectangular base. work out height mt to 1 decimal place

Given the box plot, will the mean or the median provide a better description of the center? box plot with min at 10.5, q1 at 11.5, median at 12.5, q3 at 13.5, max at 15

Need solving this second acceleration problem.