What was special about the number system used by Ibn Sina?

Three thieves agreed to rob a bank. the first was to steal a car to be used for the getaway, the second agreed to procure weapons, and the third would check the bank for cameras. the car thief stole a car and parked it in a lot behind his girlfriend's apartment building. while visiting her the night before the robbery, the car thief suffered a series of convulsive seizures. he was rushed to the hospital where he was placed in the intensive care unit and heavily sedated. meanwhile the two other thieves, unaware of their accomplice's illness, met and decided to rob the bank on their own, despite the absence of a getaway car and driver. they robbed the bank, but were quickly apprehended as they tried to escape and implicated the car thief under police questioning.the car thief can be charged with: a theft of the car only.b conspiracy to commit robbery and theft of the car only.c robbery and theft of the car only.d theft of the car, conspiracy to commit robbery, and robbery.