The list numbers contains several items each of which is a number. The program below should set a variable product to all the items in numbers multiplied together. So for example if numbers has the contents shown in the watcher below then product should be set to $210($i$.$e$.$ to $3$x$2$x$5$x$7).$

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.

a $=$ Blank $1$ Question $4$

position

b $=$ Blank $2$ Question $4$

$[$length$\_$of$[$numbers$]]-[1]$

c $=$ Blank $3$ Question $4$

item$[$product$]$of$[$numbers$]$