We have a standard General Electric stove, with an oven.
It is probably about 18-20 years old.

Over the past month, the oven was taking longer and longer
to pre-heat, and now it does NOT heat up at all, when
the function switch is set to BAKE. The bottom element
does not get hot at all now.

(However, when set to BROIL, then the TOP element heats
right up to red-hot within about 1 minute.)

We did a 'concept' test on a WORKING oven, and it appears
that when function-switch is set to BAKE, only the BOTTOM element
is what is supposed to get hot. And, when you switch it to BROIL,
then only the TOP element is supposed to get hot, right?

So, we (naively) figure that the problem lies either in:
(1) The function-switch (BAKE/TIMED-BAKE/BROIL)
(2) The bottom element is bad.

But, we know next to nothing really about oven repair. So,
our questions a

(1)Statistically, which of these two is MOST LIKELY the cause:
The function-switch or the element?

(2)Is there a third possibility? (e.g. are there an 'fuse-like' things
that are designed to burn-out/switch off in the lower-element
circuit that could instead be the problem?)

TIA...

Dave