A loan is to be paid by instalments of $$800in1-$month from now, $$600$ in $3-$months

from now, and $$500$ in

$4-$months from now. Instead of this payment scheme, the

borrower wishes to make one single payment $2$ months from now What is the

amount of the alternative single payment using a focal date of $3$ months and

simple interest $r=6\%?$