Table:
text: List of GPS satellites
Satellites by block
Satellites by block
Block Launched Operational Not_usable Retired Launch_Failures
Block I 11 0 0 10 1
Block II 9 0 0 9 0
Block IIA 19 8 1 10 0
Block IIR 13 12 0 0 1
Block IIRM 8 7 0 1 0
Block IIF 4 4 0 0 0
Total 64 31 1 30 2

Question: From GPS satellites by block list of satellites, what is the total number of launch failures if there are 4 launches and the unusable value is greater than 0?

Question: What is the average number of unusable satellites among GPS satellites when 0 are idle and launch errors are less than 1 in satellites per block?