4. Determine the number of integer solutions of x1 + x2 + x3 +
x4 = 17, where
a. xi ≥ 0, 1 ≤ i ≤ 4
b. x1, x2 ≥ 3 and x3, x4 ≥ 1
c. xi ≥ -2, 1 ≤ i ≤ 4
d. x1 , x2 , x3 > 0 and 0 < x4 ≤ 10
How many ordered quadruples (x1, x2, x3, x4) of positive
integers satisfy the conditions x1 < x2 < x3 < x4 < 15
and xi+1 − xi ≥ i for each i = 1, 2, 3.
Let U = {(x1,x2,x3,x4) ∈F4 | 2x1 = x3, x1 + x4 = 0}.
(a) Prove that U is a subspace of F4.
(b) Find a basis for U and prove that dimU = 2.
(c) Complete the basis for U in (b) to a basis of F4.
(d) Find an explicit isomorphism T : U →F2.
(e) Let T as in part (d). Find a linear map S: F4 →F2 such that
S(u) = T(u) for all u ∈...
The prices of inputs (x1,x2,x3,x4) are
(4,1,3,2):
(a) If the production function is given by f(x3,x4)
=min{x1+x2,x3+x4} what is the minimum cost of producing one unit
of output?
(b) If the production function is given by
f(x3,x4)=x1+x2 +min{x3+x4} what is the minimum cost of producing
one unit of output?
Let X1, X2, X3, and X4 be a random sample of observations from a
population with mean ? and variance ?2. Consider the following two
point estimators of ?:
b1= 0.30 X1 + 0.30 X2 + 0.30 X3 + 0.30 X4 and
b2= 0.20 X1 + 0.40 X2 + 0.40 X3 + 0.20 X4 .
Which of the following constraints is true?
A. Var(b1)/Var(b2)=0.76
B. Var(b1)Var(b2)
C. Var(b1)=Var(b2)
D. Var(b1)>Var(b2)
Using Y as the dependent variable and X1, X2, X3, X4 and X5 as
the explanatory variables, formulate an econometric model for data
that is (i) time series data (ii) cross-sectional data and (iii)
panel data – (Hint: please specify the specific model here not its
general form).
The values of X1, X2, X3, X4 and X5 are .1, .2, .08, .2 and .3.
Explicate the meaning of those numbers for the Z score. What are
the prospects of this firm? Discuss thoroughly.