The following data refers to an open belt drive: Pulley A Pulley B Purpose?. Driving Driving Diameter?. 450 mm 750 mm Angle of contact?. \[{{\theta }_{A}}\,=\,150\] \[{{\theta }_{B}}\,=\,210{}^\circ \] Coefficient of friction between belt and pulley \[{{f}_{A}}\,=\,0.36\] \[{{f}_{B}}\,=\,0.22\] The ratio of tensions may be calculated using the Relation \[({{T}_{1}}/{{T}_{2}})\,=\]exp (z) where z is:

• A. \[{{f}_{A}}{{\theta }_{A}}\] 
• B. \[{{f}_{B}}{{\theta }_{B}}\]
• C. \[({{f}_{A}}+{{f}_{B}})\,({{\theta }_{A}}+{{\theta }_{B}})/4\]  
• D. \[({{f}_{A}}{{\theta }_{A}}+{{f}_{B}}{{\theta }_{B}})/2\]