Turned knob off and oven stayed on. The bottom heating element stayed on. We had to turn it of by the circuit breaker. Tried it the next day and the bottom element still stayed on, but there was one area that was bright red and started sparking. The second day it took twice as long to make biscuits than it usually does. The bottom does not seem to be working correctly, the biscuits did not brown on the bottoms. Can you please tell me what is wrong? Also the stove came with our house and we have lived in our house 9 years and I was wondering how old the range is? Thanks for you help