first stage delta-v is: 303 s * 9.80665 m/s^2 * ln (10200 kg / 950 kg) = 7053.19 m/s

second stage delta-v is: 333 s * 9.80665 m/s^2 * ln (2300 kg / 250 kg) = 7247.06 m/s

LEO requires near 8600 m/s. So, the second stage is necessary for LEO starting from 0 m/s. The big unknowns are how much delta-v is lost to air resistance and due to the gravity of the earth (launch trajectory optimization). To calculate those would require numerical simulation, see https://space.stackexchange.com/questions/20848/how-to-deter.... Optimistically an air launch would occur at 40k' (12k metres) and 600mph (270 metres per second). The effect on the first stage only due to the imparted velocity reduces the delta-v to 6783.19 m/s or a reduction to a wet mass of 9314.03 kg (885.97 kg of fuel). 270 m/s / 7053 m/s = 0.0383.