Answer:
cost of equity = 13%
Step-by-step explanation:
With the info given, we will use cost of equity formula from Dividend Growth Model. THis is given by:

Where D_1 is the next year dividend or D_1 = D_0(1+g)
P_0 is current stock price
g is the growth rate
Since D_0 (dividend this year) is 4.20 and g = 6.4% or 0.064, we can calculate D_1:

Current share price is 68, so we can now calculate cost of equity:

Hence,
cost of equity = 13%