37 A continuous joint-and-survivor life annuity, with payments initially at a rate of $1 per annum, issued to (x) and (y), commences payments immediately, and pays $1 per annum as long as both survive. During the first 10 years, the payment rate to the survivor halves at the first death. Beyond the first 10 years, payments rise to $2 per annum if (x) only is alive, but (y) receives no payments if (x) is dead. Find the single benefit premium for the annuity, given ax=11;axy=8; ay=12;ax10j=4;ay10j=6;axy10j=2