(1) In the first quarter, the available economic income consists of two parts, one is direct economic income, and the other is indirect economic income;

Direct economic income includes training venue fees and ticket income.

Direct economic income = 20+20/0.4 = 20+50 = 700,000 yuan;

Indirect economic income = direct economic income * 2.8 = 70 * 2.8 = 1.96 million yuan;

Total economic income = 70+196 = 2.66 million yuan.

(2) The venue fee for the second quarter is X, and the venue fee for all corresponding Olympic venues in the first quarter is Y..

Equation set X=0.75Y

X= 1.25*(Y-20)

Solve the equation X=37.5 Y=50.

Growth rate =(37.5-20)/20=0.875

Total income = 266+266 * (1+0.875)+266 * (1+0.875) 2+266 * (1+0.875) 3.

=266+498.75+935. 15625+ 1753.4 179

=3453.3

~ = 34.53 million yuan