623 the following discount function contains semi-annual disceunt factors out to two years: d(0.5)=0.9970,d(1.0)=0.9911,d(1.5)=0.9809,d(2.0)=0.9706. What is the inflect eighteen-month (1.5 year) spot rate (aka, 1.5 year zero rate)? A. 0.600%