in 2021 Martha's business use of her vehicle fell to less than 30%. in prior years she used the vehicle more than 50% for business and she had been using the modified accelerated cost recovery system to recover the cost basis if this asset. What method convention and recovery period must she use in 2021? a. 150% decling balance mid month convention alternative depreciation recovery period. b. 200% declining balance half year convention general depreciation system recovery period c. straight line method mid moth alternative depreciation system recovery period d. straight line half year convention alternative depreciation system recovery period