You plan to invest your cash of $150,000 in GF and DSA securities. According to experts, the forecast for the next year is: * Rate of return of the market portfolio 15% * Rate of return on treasury bills 9% * Standard deviation of market portfolio returns 4.5% *Beta coefficient of GF stock 0.75 *DSA security beta coefficient 0.85 * The covariance between the returns of GF and DSA securities 0.0018 * Expected rates of return and standard deviations of returns for DSA and GF securities are:

Expected return	Titre GF	Titre DSA
Rendement espr	12.40%	13.25%
Standard deviation of returns	3%	6%

Calculate the beta coefficient of a portfolio composed of 50% market portfolio and 50% treasury bills.