Suppose Stan holds a portfolio consisting of a $10,000 investment in each of 8 different common stocks, equally. The portfolio's beta is 1.25. Now suppose Stan decided to sell one of his stocks that has a beta of 1.00 and to use the proceeds to buy a replacement stock with a beta of 1.35.

What is the portfolio's new beta?

PLEASE SHOW DETAILED STEPS AND FORMULAS TO GET THE ANSWER.