Christian Missions in Persia. Christianity was introduced in Persia in the Parthian period, and several bishoprics were established there (Latourette, II, pp. 263ff.).
You will likely pay more for the exchange, even if your tank is completely empty. An empty 20 lb tank will hold about 4.7 gallons of propane. That is $18.47 at $3.93 per gallon, which is the low quantity price (I just paid $3.44 per gallon when filling several tanks). The exchange is about the same price. Keep in mind this comparison is as if the exchange gives you a FULL tank.
Pricing Tank Pricing estimates for 250-, 500-, and 1,000-gallon tank sizes are shown in Figure 5. Hardware The pricing estimate for hardware pieces is $600. This estimate includes the riser and gusset ($550), and the liquid level sensing system ($50). Cost Estimates Cost estimates were made for the 250-, 500-, and 1,000-gallon size composite propane tanks. The distribution of costs across components is shown in Figure 5.