Problem Dimerization of the receptor for a growth hormone

A receptor for a growth hormone binds its ligand and then dimerizes to form a receptor/ ligand dimer according to the following scheme  

If the rate constant for this second order reaction was 0.05 nM min and there is a concentration of 20 nM of receptor/ligand present at the begiiming of the experiment, how much receptor/ligand is left after 30 minutes And how much dimer has formed after 30 minutes  

The reaction scheme for the dimerization of the receptor/ligand complex is  

R(eceptor)/L(igand) + R(eceptor)/L(igand) —Dimer We can therefore write the general rate equation for this reaction as  

We want to know, how much of the receptor/ligand complex is left after 30 minutes and therefore we are looking for RL(t). Rearranging the equation gives  

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