def estimate_yield(ndvi,evi,savi,ndre,c_type,area):
	import math	
	est_yield = -1
	if str(c_type) == '1k' or str(c_type) == '1r':
		est_yield = round(0.3419*math.exp(4.1587)*((ndvi+evi+savi+ndre)/400)*(area/10000),2)
	elif str(c_type) == '14':
		yield_per_ha = round((-0.2088+1.5212*(((ndvi+evi+savi+ndre)/400)^2))*(10000/1000),2)
		est_yield = yield_per_ha*(area/10000)
	return est_yield