The biologists measures amount of contaminant in the lake 6 hours after the chemical spill and again 10 hours after spill. She sets up 2 possible models to find Q, amount of chemical remaining in lake as the function of t, the time in hours since spill. First model suppose contaminant is leaving lake at the constant rate, which finds to be 6 tons/hour. Using this model, she evaluates that lake will be free from contaminant 35 hours after spill. Hence, she requires to determine Q(6) and Q(10). Second model supooses that amount of contaminant reduces exponentially. Determine this exponential model.