<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def jenkins_rao(target, throat_perimeter='throat.perimeter', throat_area='throat.area', throat_diameter='throat.indiameter'):
 r""" Jenkins and Rao relate the capillary pressure in an eliptical throat to the aspect ratio References Jenkins, R.G. and Rao, M.B., The effect of elliptical pores on mercury porosimetry results. Powder technology, 38(2), pp.177-180. (1984) """

    P = target[throat_perimeter]
    A = target[throat_area]
    r = target[throat_diameter]/2
    # Normalized by value for perfect circle
    value = (P/A)/(2/r)
    return value