Function describing two exponential decline functions with a break point
between them.

HS.solution(t, parent.0, k1, k2, tb)

## Arguments

t |
Time. |

parent.0 |
Starting value for the response variable at time zero. |

k1 |
First kinetic constant. |

k2 |
Second kinetic constant. |

tb |
Break point. Before this time, exponential decline according
to `k1` is calculated, after this time, exponential decline proceeds
according to `k2` . |

## Value

The value of the response variable at time `t`

.

## References

FOCUS (2006) “Guidance Document on Estimating Persistence and
Degradation Kinetics from Environmental Fate Studies on Pesticides in EU
Registration” Report of the FOCUS Work Group on Degradation Kinetics,
EC Document Reference Sanco/10058/2005 version 2.0, 434 pp,
http://esdac.jrc.ec.europa.eu/projects/degradation-kinetics

## Examples