The problem with this question is that we don't know if the interest rate of 6% is nominal or effective.
A nominal interest rate is different from the effective if the period of time after that the interest is credited (e.g. a month) is not identical to the basic time unit (normally a year).
For example, let's assume a nominal interest rate of 6% which is credited as of 6%/12 = 0.5% every month. After one year, the initial capital is increased by the factor (1+0.005)^12 = 1.0616. As a result, this nominal interest rate is equivalent to an effective interest rate of 6.16%.
Therefore, the correct calculation will consider an interest rate of 6.16% and the final result will be a monthly payment of $832.43.
On the contrary, if the 6% corresponds to an effective interest rate, the final result will be in fact $828.64.
BTW $736.11 is the value you get for simple interest, which is not the case for this is compound.