The outflow rate is given by the formula above and the inflow rate is 60 GtC yr-1 . Using Excel, calculate how the reservoir size changes with time (assume a time step of one year), beginning with a reservoir size of zero and continuing until the reservoir reaches equilibrium (equilibrium is reached when the reservoir size stops changing, i.e. the outflow rate equals the inflow rate). Plot the reservoir size as a function of time and describe the graph