Question about a stove that does not heat up

I have a Hardwick stove. One burner doesn’t work at all, and the other
three take a very long time to get hot. After half an hour, it can boil a pot of
water at a slow boil but it never gets hot enough to really boil fully.
We are thinking perhaps we can replace the burners, and that would solve the
problem. This is a narrow stove–I think 20 inches. It’s hard to say what
the model number is, but i think it’s:
878922

Also, there’s a piece of paper stuck to the back of the stove with several
schematic drawings and the following in the lower right corner [duplicated as
written]:

878922 [enclosed in a box]

EC-170

IE-436-091-99

Rev. A

I-83

Do you have a suggestion as to what I need to order to fix the problem? It’s quite an old stove so I don’t want to spend too much money on it, however I’d love to fix it, if it’s possible.
Thanks very much for your help.
Regards

Maria

Cannot find any info on this unit.

You may be able to find an element by calling or emailing AppliancePartsPros.
Remove it and check that it has continuity with a meter.

I cannot see the other 3 all going bad at the same time.
Check the power going to the unit.
I am guessing that it should be 240 volts perhaps you have lost half the line and are only getting 120 volts.
Note the oven would also heat slowly or not at all.
Could try turning the breaker off/on slowly a couple times.