oven will not heat

My oven heats very slowly (takes 30-45 minutes to reach 285 degrees)and will never get above 300 degrees. How can this problem be fixed?

Thanks

Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=SVD48600P

Check that both elements are coming on.
Most units switch back and forth between the elements when preheating so if one element is shot it will never reach set point temperature or will take a long time.

If the unit is coming ready but the temperature is low check the oven sensor.
Below is a good link, see Items 7, 8, 20 and 21.
http://www.applianceaid.com/elecrange.html

If you remove an element to check it with a meter be sure to unplug or remove power from the unit as one side of the element is always live, even with the oven shut off.