Please note that in respect of unexplained cash credits section 68 & 115BBE are applied as stated in the act. Section 68, provided to add the unexplained cash to the income of assessee AND section 115BBE provides for manner of calculation of tax on such income as explained below:-
From the reading of section 68, following conditions can be stated to attract the applicability of section 68 :-

1. Assessee has maintained ‘books’.
2. There has to be credit of amounts in the books maintained by the taxpayer of a sum during the year.
3. The taxpayer offers no explanation about the nature and source of such credit found in the books or the explanation offered by the taxpayer in the opinion of the Assessing Officer is not satisfactory.

If all the above conditions exist, sum so credited may be charged to tax as income of the taxpayer of that year. Hence if you offer no explanation or unsatisfactory explanation for this cash transaction then section 68 may be applied. 
 
As per Section 115BBE, income tax shall be calculated at 60% where the total income of assessee includes following income:- 
(a) Income referred to in Section 68, Section 69, Section 69A, Section 69B, Section 69C or Section 69D and reflected in the return of income furnished under Section 139; or
(b) Which is determined by the Assessing Officer and includes any income referred to in Section 68, Section 69, Section 69A, Section 69B, Section 69C or Section 69D, if such income is not covered under clause (a).
Such tax rate of 60% will be further increased by 25% surcharge, 6% penalty, i.e., the final tax rate comes out to be 83.25% (including cess). Provided that such 6% penalty shall not be levied when the income under Section 68, 69, etc., has been included in return of income and tax has been paid on or before the end of relevant previous year.

No deduction in respect of any expenditure or allowance [or set off of any loss] shall be allowed to the assessee in computing his income referred to in clause (a) of sub-section (1) of Section 115BBE.

if you have proper explanation for the cash credit then neither section 68 nor 115BBE ….both will not apply.