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(ii) in the case of Model III,<br />

1<br />

1 - a<br />

(30) B = 1 - a,<br />

C = 1 log 1 - « + Tp^-3 + 7. rj-<br />

1 - a (1 - a)- 1 (1 — aY<br />

Furthermore, the solution is unique.<br />

OPTIMAL INVESTMENT 593<br />

In proving this theorem, we shall make use of the following lemma and corollaries.<br />

LEMMA: Let u(c), {ft}, and r be defined as in Section 2 and let v = {v2,..., vM)<br />

be a vector of real numbers. Then the function<br />

(31) h{v2,v3,...,vu) = E<br />

subject to the constraints<br />

(27) D.-SSO, i ol = 1<br />

where v[ 5= 0 for all i 4 S.<br />

Now consider the point v l = v° + Xv' = Xv' where A Js 0 and o' is one of the<br />

points in this neighborhood. Let b{v) be the greatest lower bound on b such that<br />

Prj I 0?i - r)f, < b\ > 0.<br />

7 The author gratefully acknowledges a debt to Professor George W. Brown for several valuable<br />

suggestions concerning the proof of the closure and the boundedness of D.<br />

OPTIMAL CAPITAL ACCUMULATION AND PORTFOLIO SELECTION

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