(i) My diagram looks like as below

(ii) In #Delta ADC#, after converting all distances to meters.

#tan alpha=(CD)/20000#

#=>CD=2.0xx10^4tan alpha " meter"#

(iii) We make use of cosine rule.

For a triangle with sides #a,b and c# and angles #A, B and C# the cosine rule states:

#a^2 = b^2 + c^2 - 2bc cos A#

Applying in #DeltaABC# where #angle A=120^@#

#BC^2 = (2.0xx10^4)^2 + (1.0xx10^4)^2 - 2xx2.0xx10^4xx1.0xx10^4 cos 120^@#

We know that #cos120^@=-1/2#

#=>BC^2 = 4.0xx10^8 + 1.0xx10^8 + 2.0xx10^8#

#=>BC^2 = 7.0xx10^8 #

#=>BC = sqrt(7.0xx10^8) #

#=>BC = sqrt7xx10^4 " meter"#

(iv) In #DeltaBDC#

#tan25^@15'=(CD)/(BC)#

Making use of values found in (ii) and (iii)

#tan25^@15'=(2.0xx10^4tan alpha)/(sqrt7xx10^4)#

Solving for #alpha#

#tan alpha=sqrt7 /2tan25^@15'#

#alpha=tan^-1(0.6239)#

#alphaapprox32^@#, correct to nearest degree.