3.使用氧乙炔鋅接時，若鋅炬操作不當或器具缺陷，會引起火焰產生爆裂聲的回火(back fire)現象，請說明3種主要回火的原因與對策。(10分)

III. What value is represented by the bit pattern 01101111 when interpreted using a floating-point format where the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa? (10%)