The list 10km_times contains times, in minutes, taken by runners to run a 10km race. The when[space]key_pressed script below should calculate and display the average (mean) of the times in the list, or tell the user that the list is empty. So for example if 10km_times has the contents shown in the watcher below then the message 'Average time in minutes is 52.6' should be displayed.

The program is incomplete at the points labelled a, b and c. Select the code (in textual form) that should be inserted at each of these points.

[total]+[item[position]of[10km_times]] item[total]of[10km_times] 10km_times position item[position]of[10km_times] length_of[10km_times]

a = ?

b = ?

c = ?