A large deep lake, which initially had a uniform oxygen concentration of 1kg/m 3 , has its surface concentration suddenly raised and maintained at 9 kg/m 3 concentration level. Reduce the general...

A large deep lake, which initially had a uniform oxygen concentration of 1kg/m³, has its surface concentration suddenly raised and maintained at 9 kg/m³
concentration level. Reduce the general differential equation for mass transfer to write the specific differential equation for

a. the transfer of oxygen into the lake without the presence of a chemical reaction;

b. the transfer of oxygen into the lake that occurs with the simultaneous disappearance of oxygen by a first-order biological reaction.